NlpR controls genes involved in nitrogen and lipid metabolism in oleaginous Rhodococcus strains

HERNANDEZ MA; ALVAREZ HM

Rosario

Congreso; XLX Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2014

SAIB

Oleaginous Rhodococcus strains are able to accumulate large amounts of triacylglycerols (TAG) under nitrogen-limiting conditions from a broad range of carbon sources. Studies to establish physiological and molecular mechanisms for TAG biosynthesis and accumulation have been reported, but so far the regulatory aspects of these processes are unknown in such bacteria. In this work, we described NlpR (Nitrogen-lipid Regulator) as a putative transcriptional regulator which controls the expression of genes involved in nitrogen and lipid metabolism in R. jostii RHA1 and R. opacus PD630. Transcriptome analyses showed a higher expression of nlpR under nitrogen-limiting conditions, but it was repressed when an inhibitor (cerulenin) of the novo fatty acid biosynthesis was added. NlpR disruption resulted in a significant decrease of TAG content besides to a delayed growth with NO3- or NO2-; whereas its overexpression led to an improved TAG accumulation under nitrogen-rich conditions. Preliminary analyses by EMSA assays, showed a positive binding of purified NlpR to the upstream region of genes involved in NO2- assimilation (nasK-nirB) and TAG biosynthesis (atf1) among others lipid metabolism genes of RHA1 strain. The results of this work suggest that NlpR acts as a global regulator linking the nitrogen and lipid metabolism in response to nitrogen starvation conditions in oleaginous rhodococci.